Aerodynamic admittance of a two-dimensional body

The unsteady load response in the frequency domain for a general two-dimensional body has been determined. Systems with one degree of freedom have been considered. The theory is based on the potential incompressible flow, and resolves around a mathematical treatment that starts from the theory of Drischler and Diederich. Admittance for the lift force and pitching moment (or side force and yawing moment for non lifting systems) has been calculated in closed form or numerically for aerofoils, swept back and swept forward wings, delta wings, and some ground vehicles (various car shapes) using sinusoidal and square gusts. Simulations have been performed for a wide range of gust speed ratios. The general features of the admittance function are discussed. It is proved that for some geometries there is an large number of frequencies that yield critical damping. These frequencies are generally very high. Comparisons with existing experimental data are good in the whole range of practical frequencies.